Back in 2006, Matt Cutts suggested that by adding [-inurl:html -inurl:htm] to your query you can restrict Google search results to homepages.
Now, Google allows to restrict search results to homepages for blogs: "We've updated Google Blog Search to make it easier to find blogs that match your query, instead of just finding blog posts. The blogs tool on Google search results filters your results so you see only blog posts. We've added a homepages option that shows a full set of blogs related to your query," informs Jeremy Hylton in a Buzz post."
In short, you can find more blogs by clicking on the "homepages" filter from Google's sidebar, when you query Google Blog Search.